As related to Flynn case the Supreme court has already decided unanimously:

Ginsburg Rebukes 9th Circuit Panel for 'Radical Transformation' of Appeal

The principle of "party presentation" refers to a long-standing feature of the court system that the parties in litigation, and not judges, are responsible for raising the legal issues a court must resolve.

https://www.law.com/nationallawjournal/2020/05/07/ginsburg-rebukes-9th-circuit-panel-for-radical-transformation-of-appeal/?slreturn=20200413071733#

Supreme Court has already decided unanimously that what judge in Flynn case is inappropriate and rebuked the 9th circuit for it recently.

https://www.law.com/nationallawjournal/2020/05/07/ginsburg-rebukes-9th-circuit-panel-for-radical-transformation-of-appeal/?slreturn=20200413071733#